1. Field of the Invention
This invention generally relates to a linear motion guide unit suitable for use in moving parts of machining tools, precision processing apparatuses and test apparatuses, and, in particular, to a linear motion guide unit having an anti-vibration or a braking function. More specifically, the present invention relates to a sliding contact type linear motion guide unit having a sliding contact between a rail and a slider.
2. Description of the Prior Art
A linear motion guide unit having a braking function and/or an anti-vibration function is well known in the art and is typically described in the Japanese Utility Model Laid-open Pub. No. 58-6010 and the Japanese Pat. Laid-open Pub. No. 61-116119. As illustrated in these publications, a typical linear motion guide unit having a braking function and/or an anti-vibration function includes a rail, a slider, a plurality of rolling members interposed between the rail and the slider, and a frictional member also interposed between the rail and the slider. Another such prior art linear motion guide unit includes a rail, a pair of end sliders, a plurality of rolling members interposed between each of the end sliders and the rail, an intermediate slider located between the pair of end sliders, and a small gap defined between the rail and the intermediate slider and filled with a lubricant, thereby serving as a fluidic damper.
However, in the former prior art structure, since the rolling members and the frictional member are both incorporated in the single slider, the mounting location of the frictional member is limited, which in turn causes limitations in its braking function and/or its anti-vibration function, and the structure is complicated and thus difficult to manufacture. On the other hand, in the latter fluidic damper case, there still remains difficulty in maintaining the lubricant between the rail and the slider without significant leaks and thus this technique lacks practicality.